1. Field of the Invention
The present invention relates to a dandy roll useful in producing paper bearing a watermark having a grid pattern of translucent lines and repeating translucent diamond shapes at alternating intersections of the lines.
2. Introduction
In papermaking, watermarks are conventionally formed by contacting the paper stock while it is still damp with a dandy roll having raised and/or recessed areas on the surface. An opaque mark known as a "shaded mark" is formed on the paper in areas contacting the recesses on the surface of the dandy roll and is the result of pulp fibers accumulating in the recesses as the paper stock travels under the dandy roll on the papermaking machine. Translucent marks, known as "wire marks," are formed in the paper in areas contacting the raised areas on the surface of the dandy roll. These marks are the result of the raised surface of the roll displacing the fibers in the stock resulting in areas in which the fibers are less concentrated and the paper is more translucent.
It is conventional in the art to form shaded marks by depressing the surface of the wire screen forming the dandy roll and to form wire marks by soldering wire segments, known as electro wires, to the surface of the dandy roll screen. See, for example, U.S. Pat. No. 353,666 to Z. Crane, Jr. (1886) and U.S. Pat. No. 1,571,715 to Fearing (1926). It has also been known to watermark paper by altering the draining rate of the Fourdrinier screen by modifying the weave in the screen such as by using larger gauge wire to form the screen or by omitting a wire from the screen altogether. See, for example, U.S. Pat. No. 1,616,222 to Harrigan (1927).
U.S. Pat. No. 4,526,652 to Waters, discloses a papermaking process wherein paper bearing the look of an oxford cloth weave is produced. The oxford cloth simulation is achieved by positioning narrow pockets and electro wires along the circumferential and longitudinal axis of a plain weave dandy roll screen.
U.S. Pat. No. 5,100,512 to Waters, discloses a papermaking process wherein paper bearing a unique watermark is produced using a dandy roll having a screen in which the widthwise fill (shute) wires are woven in a one over then two under pattern with lengthwise warp wires such that a longer warp knuckle results on the side of the screen in contact with the passing paper stock.